Manufacturers and operators of vehicles are constantly seeking to improve the fuel efficiency of their vehicles. For vehicles that utilize internal combustion engine, increasing fuel efficiency results in lower operating costs for the customer and increased vehicle range. Increased fuel efficiency can also reduce vehicle emissions.
One strategy for improving fuel efficiency is to reduce vehicle idle time. During normal operation, vehicles experience periods in which the vehicle is not moving, but the engine in idling. Idling conditions can occur when a vehicle is being operated in heavy traffic or as a result of traffic signals, such as stop signs, stop lights, railroad crossings, etc. In order to reduce vehicle idle time, various systems and methods have been developed to automatically (1) stop the engine when the vehicle is stationary and certain operating conditions are met and (2) restart the engine based on operator input and/or other operating conditions. By reducing the time during which the vehicle engine operates unnecessarily, fuel consumption is reduced, and vehicle fuel efficiency is increased. One system for reducing vehicle idle time is disclosed in PCT Patent Application Publication No. WO2016014396 A1, filed Jul. 20, 2015, the disclosure of which is incorporated herein by reference.
When known systems automatically stop the engine during an idle condition, the engine must come to a complete stop before the engine is restarted. That is, the engine speed (Veng) must drop to 0 revolutions per minute (rpm), after which the vehicle starter is utilized to restart the engine in the same manner as under a normal starting operation. As a result, if the vehicle operator tries to move the vehicle before the engine speed has reached 0 rpm, there is a delay between the operator requesting a restart and the engine restart sequence beginning. In order to reduce operator frustration caused by this delay and to improve vehicle performance, the presently disclosed stop/start system reduces and/or eliminates this delay.